Great advancements have been made in semiconductor technology in the last few years largely due to the discovery of new materials and the discovery of new methods of making better materials. These advances have led to new device applications for semiconducting materials and such applications often require different fabrication techniques. Typically, these techniques are aimed towards obtaining smaller size, more precise location of various geometrical features in the device, more accurate shapes for various geometrical features in the structure, greater adherence of metallic substances to semiconductive surfaces, etc.
A particular case in point with regard to gallium arsenide devices is dicing of wafers so as to separate individual semiconductor devices. This is particularly important for gallium arsenide light-emitting devices where anisotropic etching is highly advantageous so as to reduce the amount of material etched.
In fabricating such devices it would be highly advantageous to have an etching procedure which can be controlled as to etch rate, area to be etched, geometrical shape etched, etc. Such an etching procedure is usually referred to as an anisotropic etching procedure. Such a procedure would be useful for making channels, via holes, mirrors, lenses, diffraction gratings, and in the separation of individual chips on a semiconductor wafer.
Photoetching has been carried out on n-type indium phosphide using ferric chloride solution (see D. Lubzens, Electronics Letters, Vol. 13, page 171 (1977)). Photoetching of gallium arsenide has been described by F. Kuhn-Kuhnenfeld in an article entitled "Selective Photoetching of Gallium Arsenide" published in Journal of the Electrochemical Society: Solid-State Science and Technology, page 1063 (August 1972) and Zh. I. Alferov et al, "Diffraction Gratings Produced on a GaAs Surface by Interference Photoetching," Soviet Physics Technical Physics, Vol. 21, No. 7, page 857 (July 1976).